More #SNESmusic vastness amusement:
The SNES' audio processing unit ( https://en.wikipedia.org/wiki/Nintendo_S-SMP ) holds 64KB of RAM for storing sample data, the echo buffer, and such.
An SPC file is essentially just a small metadata chunk tacked onto a memory dump of that RAM. This means that every SPC is 64KB plus a tiny bit. Within a single game's soundtrack, most of that data is repeated in each track, so it compresses well.
The 7Zip archives take up 173MB.
Unpacked, these total well over 2GB.